Lead pencil and method of making same



- Jan. 1, 1935- GRQSSMAN v 1,985,894

LEAD New AND METHOD OF MAKING sum Filed Jul 's. 195s Patented Jan. 1,1935 PATENT OFFICE LEAD PENCIL AND METHOD or MAKING SAME Hamid Grossman,Caldwell, N. 1., assignor to American Lead Pencil Company, Hoboken, N.1., a corporation of New York Application July s, 1933, Serial No.678,993

11 Claims. (01. 120-83) f of wood or similar fibrous substance; and saidinvention relates more particularly to the treatment of the rods ofmarking material or leads in such manner as to insure a strong andlasting bond between the lead and its enclosing sheath.

The leads or rods of marking material used in pencils of the typereferred to are of varying composition; but usually they comprise inadmixture with graphite or other marking material a certain quantity ofan organic compound,

such as a waxy, oily or greasy substancetallow or stearic acid, forexample-which conduces to I0 cements will adhere.

One object of the present invention is to effect a strong and lastingbond between the lead and its sheath, which object, together with otherobjects of the invention, I accomplish by reacting upon the surface ofthe waxy or greasy lead with an agent, such as chromic acid, whichoxidizes the organic substances exposed on the surface, withoutiniuriously affecting the marking substance, forming soluble salts andoxidation products which are soluble in water and easily removed bywashing. This step of the process may be satisfactorily andexpeditiously performed by placing the leads in dipping cans andimmersing them for a short time, say from two to five minutes, in a bathof chromic acid solution, formed, for example, by dissolving a chromate,such as sodium bi-chromate, in sulphuric acid. This exposure of theleadsto an acid capable of oxidizing the organic substances on thesurface thereof should not be prolonged beyond the time required toeffect such oxidation. since a longer exposure might result inundesirable reactions.

The leads are then washed in water to remove all acids and reactionproducts. Water washing sumces'for this purpose; but if desired theleads,

to grease, forming a coating towhich glues and after washing in water,may be immersed in an alkaline bath such as sodium carbonate, therebyinsuring the neutralization of any remaining acid. It is highlydesirable that all traces of acid be removed, not only to preventdeleterious effect 5 upon the leads, but also because it is not safe toput a lead containing acid to the mouth. Further, the absence of acidsand other foreign matter conduces to the formation of a better bond. Itis one of the advantages of the present process that it leaves no acidresiduum, even when no alkaline neutralizer is used. Where anintervening impervious coating between the lead and the sheath is usedsome of the acid is unavoidably shut into surface pores of the lead.

By means of the process herein described the surface of the lead isbrought into a condition which insures a satisfactory, a strong and alasting bond, since the glue adheres directly to the lead, without theinterposition of a coating of any sort. On the other hand, where a,chemically formed coating is interposed, if the' latter does not adhereproperly to the lead, no bond is effected, or at best an imperfect bond,between the lead and the glue.

The accompanying drawing comprises a perspective view, partly intransverse section, illustrating a portion of a pencil made inaccordance with the present invention. In said drawing, 1 is the leadhaving its surface degreased in the manner described herein; 2, 2, arethe two sections of the wooden sheath; and 3 is the glue applied to thedegreased surface of the lead and by which said lead is secured to thewooden sheath.

What is claimed is-- 1.The method of making pencils consisting inremoving surface grease from the lead containing greasy material by anagent such as chromic acid, washing the lead, and attaching the woodensheath to the lead by adhesive applied directly to said degreasedsurface of the lead. i

2. The method of making pencils consisting in removing surface greasefrom the leadv containing greasyonaterial by an agent which oxidizessaid surface grease, washing the lead, and attaching the wooden sheathto the lead by adhesive applied directly to said degreased surface ofthe lead.

3. The method of making pencils by treating leads which contain greasymaterial with chromic acid thereby breaking down the greasy substanceexposed on the surface of the leads, washing the wad and attaching thesheath to the lead by adhesive applied directly to said .deg'reasedsurface.

4. The method of making pencils by treating leads which contain greasymaterial with chromic acid thereby breaking down the greasy substanceexposed on the surface of the leads, washing the leads by immersing themin an alkaline bath, and attaching the sheath to the lead by adhesiveapplied directly to said degreased surface.

5. As a new article of manufacture, a pencil comprising a core ofmarking material containing in the interior thereof greasy organicsubstance commingled therewith but having its surface substantially freefrom grease, and a sheath attached to said core by adhesive applieddirectly to its said surface. v

6. In the process of making pencils, the step of surface treating greasypencil leads which comprises oxidizing the greasy surface to destroy itsgreasy characteristics.

7. In the process of making pencils, the steps of surface treatment ofgreasy pencil leads which comprise oxidizing the greasy surface todestroy its greasy characteristics and then washing.

with an agent capable of oxidizing surface grease to form solubleorganic reaction products.

10. In the process of making pencils, the step of treating pencil leadsto degrease the surface thereof which comprises immersing the leads in asulphuric acid solution containing an agent capable of liberatingoxygen.

11. The method of making pencils by treating leads which contain greasymaterial with chromic acid thereby breaking down the greasy substanceexposed on the surface of the leads, removing from the surface of theleads the products of the action of the chromic acid and attaching thesheath to the lead by adhesive applied directly to said degreasedsurface.

- HAROLD GROSSMAN.

